1. Field of the Invention
The present invention relates to touch panels and, particularly, to a carbon nanotube based touch panel and a display device using the same.
2. Discussion of Related Art
Following the advancement in recent years of various electronic apparatuses, such as mobile phones, car navigation systems and the like, toward high performance and diversification, there has been continuous growth in the number of electronic apparatuses equipped with optically transparent touch panels at the front of their respective display devices (e.g., liquid crystal panels). A user of any such electronic apparatus operates it by pressing or touching the touch panel with a finger, a pen, stylus, or another like tool while visually observing the display device through the touch panel. Therefore, a demand exists for touch panels that are provide superior in visibility and reliable operation.
Up to the present time, different types of touch panels, including resistance, capacitance, infrared, and surface sound-wave types have been developed. Due to their higher accuracy and low-cost of production thereof, the resistance-type touch panels have been widely used.
A conventional resistance-type touch panel includes an upper substrate, a lower substrate, and a plurality of dot spacers. The upper substrate includes an optically transparent upper conductive layer formed on a lower surface thereof, and two upper electrodes connected to the optically transparent upper conductive layer at two edges along the X direction respectively. The lower substrate includes an optically transparent lower conductive layer formed on an upper surface thereof, and two lower electrodes connected to the optically transparent upper conductive layer at two edges along the Y direction respectively. The plurality of dot spacers is formed between the optically transparent upper conductive layer and the optically transparent lower conductive layer. The upper substrate is a transparent and flexible film/plate. The lower substrate is a transparent and rigid plate made of glass. The optically transparent upper conductive layer and the optically transparent lower conductive layer are formed of conductive indium tin oxide (ITO). The upper electrodes and the lower electrodes are formed by silver paste layers.
In operation, an upper surface of the upper substrate is pressed with a finger, a pen or the like tool, and visual observation of a screen on the display device provided on a back side of the touch panel is allowed. This causes the upper substrate to be deformed, and the upper conductive layer thus comes in contact with the lower conductive layer at the position where pressing occurs. Voltages are applied successively from an electronic circuit to the optically transparent upper conductive layer and the optically transparent lower conductive layer. Thus, the deformed position can be detected by the electronic circuit.
In roll-to-roll technology, e-papers, flexible liquid crystal displays, and flexible organic light emitting displays (OLEDs) have been developed. Accordingly, the touch panel used with the flexible display should be flexible too. However, the lower substrate of the touch panel is rigid and the ITO layer has generally poor mechanical durability, low chemical endurance, and uneven resistance over an entire area of the touch panel. As such, the conventional touch panel is unsuitable for use with a flexible display. Additionally, the ITO layer has relatively low transparency in a humid environment. All the above-mentioned problems of the ITO layer tend to yield a touch panel with relatively low sensitivity, accuracy, and brightness. Furthermore, the ITO layer is generally formed by means of ion-beam sputtering, and this method is relatively complicated.
What is needed, therefore, is to provide a flexible touch panel and a display device using the same having good durability, high sensitivity, accuracy, and brightness.